This invention relates to polyolefinic polymers having improved properties. In particular this invention relates to improving the slip and ink adhesion of polyolefinic compositions. An important aspect of this invention is a polyolefinic composition containing an N-substituted lactamide and having improved adhesion to water-based ink.
Olefin homopolymers and copolymers are of commercial importance for the manufacture of numerous articles such as films and other items. In order to be useful for many of these functions it is desirable that the polyolefinic composition have good slip characteristics. This can be determined by measuring the coefficient of friction of the polyolefin. It is also important that the polyolefinic composition have good printability and adhesion to water-based inks, as these become more widely used in industries that engage in printing on them.
In order to obtain a satisfactorily low coefficient of friction, often slip agents are added to the polyolefin to lower its coefficient of friction below about 0.5, preferably below 0.3. Many slip agents and other additives for polyolefins are disclosed in the literature. These additives will lower the coefficient of friction of the polyolefin to desired levels, permitting ready handling of shaped articles and films prepared from the polyolefinic material. Polyolefinic polymers having poor slip characteristics are difficult to handle when the polymer is manufactured in the customary manner of large rolls. During storage and subsequent processing, the low slip films tend to adhere layer to layer or block together. Also such films can encounter large frictional forces in processing equipment that often cause distortions and even tearing of the film, especially when using thin film.
Haeske et al U.S. Pat. No. 3,266,924 discloses the blending of a mixture of finely divided siliceous material and a fatty acid amide slip agent into polyethylene to enhance its slip and blocking properties. Ross et al U.S. Pat. No. 3,326,840 discloses the incorporation of a small amount of a mono-N-substituted saturated carboxylic acid amide of the formula: ##STR2## wherein R is an aliphatic acyl radical having from 12 to 30 carbon atoms and R' is an aliphatic group having from 1 to 6 carbon atoms, especially an alkylol group, into a copolymer of ethylene and an aliphatic ethylenically unsaturated carboxylic ester to improve its resistance to blocking and improve its slip properties.
Foster U.S. Pat. No. 3,647,738 discloses blending an amide having the formula: ##STR3## wherein R is an alkenyl radical having 18 to about 22 carbon atoms and R' is a divalent hydrocarbon radical containing 3 to 15 carbon atoms with an alpha-olefin polymer composition to provide compositions having low blocking and no bloom characteristics and high slip properties.
While the foregoing patents and other literature disclose a variety of additives that improve the slip and/or blocking properties of polyolefins, it is also necessary that the polyolefinic compositions containing the slip agents have excellent ink adhesion, particularly to water based inks and printability so that the molded article, film or other item made from the polymer can be suitably printed. Of late it has become highly desirable for environmental reasons, such as to reduce emissions of volatile organic compounds, that the inks used to print on the polyethylene composition be water-based inks.
Accordingly it is an object of the present invention to improve the slip properties of polyolefins.
Still another object of the present invention is to improve the adhesion of water based inks to polyolefins.
Still another object of the present invention is to improve the ink adhesion of water-based inks to polyolefins containing materials for improving the slip properties of the polyolefins.
Also an object of the present invention is the prevention of polyolefin films from adhering to each other during storage.
Another object of the present invention is to impart the desired slip, printability and adhesion to water-based inks to polyolefin compositions without adversely affecting the optical properties of the polyolefin.
Other objects of the present invention will become apparent from the ensuing description.